A side air-bag is an air-bag which initially is stored within part of a vehicle seat, typically the back-rest of the vehicle seat, or in a side part of the vehicle adjacent the seat.
A side air-bag is of particular value in a side impact situation and, as is known, air-bags which are to provide protection for an occupant of a vehicle during a side impact must be inflated extremely swiftly. Consequently it is desirable for such air-bags to require a minimum amount of gas to inflate.
Various types of side air-bag have been proposed previously.
Many prior proposed side air-bags are so-called “two-dimensional” air-bags. A two-dimensional air-bag is formed from two superimposed layers of fabric of identical size and shape that are secured together at their common periphery to form an air-bag which, in the uninflated state, can be laid out flat. The two superimposed layers may be stitched together with a peripheral seam or, alternatively, a one-piece weaving process may be utilized to produce an air-bag of corresponding form, again having two superimposed layers of identical size and shape that are secured together at their periphery.
In spite of the fact that a side air-bag should be inflated with a minimum amount of gas in order to facilitate rapid inflation, it is also desirable that a side air-bag should have substantial “depth” so that, upon inflation, the air-bag will engage with a seat occupant as soon as possible and provide a maximum lateral “cushion” to protect an occupant in a side impact situation.
A two-dimensional air-bag can be inflated until the opposed sides of the air-bag bulge outwardly away from each other, providing depth or thickness for the air-bag. As the air-bag is inflated in this way, a substantial amount of gas has to be injected into the air-bag, creating an almost cylindrical form, and resulting in the pressure of gas in the air-bag quite high. When inflated in this way, the air-bag may not provide the desired cushioning effect but, instead may cause a seat occupant to “bounce” off the air-bag.
It has been proposed to provide a side air-bag which is a two-dimensional air-bag of the type discussed above. The air-bag has a transverse seam in a central region dividing the air-bag into an upper inflatable region or chamber and a lower inflatable region or chamber. The two inflatable regions or chambers each have a thickness or depth, but near the seam, each has a much lower thickness or depth. The presence of the central seam helps minimize the amount of gas needed to fully inflate the air-bag. Also, the presence of the seam may make it possible, as appropriate, to inflate the two chambers to different internal pressures. However, the presence of the seam in the two-dimensional air-bag means that the overall thickness of the inflatable region or chamber of the air-bag, when it is inflated, is rather small.
It is an object of the present invention to provide an improved side air-bag for a motor vehicle.